The present disclosure generally relates to universal serial bus (USB) systems.
Universal serial bus (USB) systems, widely used as an interfacing tool with peripheral devices of computer systems, recently are operable in situations involving plug-and-play (PnP), automatic allocation of identification (ID), and hot plugging functions. A USB cable is usually organized of four lines only, that is, two signal lines, a power source line, and a ground line. Thus, it is possible to fabricate small USB cables and small connectors, which reduces product cost and which further enables developing inexpensive peripheral devices.
According to ‘USB specification Revision 2.0 (Apr. 4, 2000)’, a high speed mode supports data transmission at the rate of 480 Mb/s, and low and full speed modes support 1.25 Mb/s and 12 Mb/s, respectively.
The USB host and device are active in one of several operation modes. This one operation mode is set by initializing with a predetermined configuration when the USB device links to the USB host. For smooth data communication between the USB host and device after initialization, it needs only to correctly execute the initialization.